Used permissions:
Phone state: Used to pause during a call. Otherwise it would only be muted by the system.
Wake lock: So the playback isn't stopped when you turn off the screen. Also for some optional features like disabling the auto screen off during playback.
Disable keyguard: In case you only want to use the app's lock screen. (And not return to the default one afterwards.)
Write/delete external storage: For some internal files in .MortPlayer, e.g. cached folder covers from ID3 tags and track order lists.
Internet: Ads (AdMob)
Boot completed: To reschedule the alarm clock after boot.
Tasks: For "StopService" activity, to avoid the system returns to player afterwards